The methods hitherto proposed to prepare a laminate semiconductor layer by liquid phase epitaxial growth from a plurality of metals belonging to the Groups III to V such as GaAs and Al.sub.x Ga.sub.1-x As include the Nelson's method, slide boat method and boat rotation method. These methods are all based on the principle of intermittently moving a plurality of tanks containing different kinds of epitaxial growth solution each having a prescribed composition, thereby successively bringing said epitaxial growth solutions into contact with the surface of a crystalline substrate. An example of the prior methods is set forth in, for example, a report by B. I. Miller et al appearing in "Journal of Applied Physics" vol. 43, No. 6, June 1972. The method proposed in said publication is of the slide boat type. There will now be described by reference to FIG. 1 this slide boat method. FIG. 1 is a fractional longitudinal sectional view of the prior art liquid phase epitaxial growth device. A crystalline substrate 6 is received in a substrate hole 5 bored in the upper surface of a substrate carrier 2. Closely mounted on said surface is a horizontally slidable solution tank holder 1 which contains a plurality of solution tanks 3a, 3b, 3c, 3d each open at the bottom and filled with solutions 4a, 4b, 4c, 4d respectively. A keep plate 7 is placed on the upper surface of the solution tank holder 1 so as to admit of the sliding thereof, and further fixed to the substrate carrier 2 by means of tungsten wires 8.
Where a laminate semiconductor layer is epitaxially grown in liquid phase by the conventional device of FIG. 1, the device is maintained at a prescribed temperature and filled with a reducing or inert gas. Where a laminate liquid phase epitaxial growth wafer is prepared, the solution tank holder 1 is intermittently carried from the right to the left in FIG. 1 to bring the solutions 4a, 4b, 4c, 4d into contact with the crystalline substrate in turn, thereby epitaxially growing a laminate semiconductor layer in liquid phase in the surface of the crystalline substrate.
However, the above-mentioned prior method has two noticeable drawbacks as described below. The first drawback is that where different solutions are epitaxially grown in liquid phase one after another, the solution tank holder 1 is intermittently moved to wipe off the unnecessary portion of the preceding liquid phase epitaxial growth solution deposited on the substrate surface by the bottom plate of said holder 1, resulting in the occurrence of scratches on the surface of said deposited layer; and that particularly with a light-emitting laminate epitaxially grown wafer, appearance of such scratches, however slight, imparts a decisive damage to the effective life and other properties of the resultant device. The second drawback is that where the epitaxial growth solutions are brought to the crystalline substrate 6 one after another, the surface of each epitaxially grown component of the laminate semiconductor layer is exposed to an inert or reducing gas; and that the inert or reducing gas, however purified, contains a minute amount of impurity, for example, oxygen, and therefore exposure of each epitaxially grown component to such impure inert or reducing gas, however, momentary, gives rise to various defects in the interface between the laminated epitaxially grown components. As the result, where an element such as a semiconductor laser is cut out from such epitaxially grown wafer, the yield will be decreased, and the life of the element will be subject to a condsiderable harmful effect.
It is known that the properties and life of, for example, a semiconductor laser and light-emitting diode is very sensitively affected by the condition of a hetero-junction. However, the above-mentioned prior liquid phase epitaxial growth method presents difficulties in suppressing the occurrence of minute scratches on each epitaxial grown component deposited on the crystalline substrate when the unnecessary portion of said component is wiped off by the bottom plate of the solution tank holder, and also fails to prevent the surface of each epitaxially grown component from exposure to an ambient impure inert or reducing gas, resulting in the appearance of irregularities on the surface of the epitaxially grown deposit.
This invention has been accomplished with the view of eliminating the above-mentioned drawbacks of the prior liquid phase epitaxial growth methods, and is intended to provide a method of epitaxially growing a laminate semiconductor layer in liquid phase and apparatus thereof which suppress the occurrence of scratches on the respective epitaxially grown formations and prevent their exposure to an ambient gaseous atmosphere while they are deposited on the substrate one after another.